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P-Mag Test Switches, necessary?

apkp777

apkp777

Well Known Member
Hey all,

Got my dual P-mags today. Currently I have two breakers (one for each) installed and no test-switches. The installation instructions call for test switches. However, are they really necessary? Why not just use the breakers? How often do you test your P-Mags for self generation?

Obviously no big deal to install a set of switches. Just can't think of a downside using breakers only.
 
im not using any nor do I have breakers. I have mine wired through fuses only and will use the master switch to secure power to test the internal gen feature right after start up. My goal is to keep switches to an absolute minimum.
 
I don't know how frequently you check your E-mags, but breakers are not switches. They will wear out. Even the kind you can't manually pull wear out because they are mechanical, operated using a spring and a built in catch. Pullable CB's shouldn't be used as a switch (unless something is wrong). Any toggle, rocker, push-button, etc. switch rated for the load and voltage should work fine.
 
RV8R999 said:
...... will use the master switch to secure power to test the internal gen.....
Click to expand...

ME, too. I am using breakers for fault protection. But plan on just dumping the main buss to check self powering of the Pmag. in reality, I plan on testing the self power feature multiple times during phase 1 and then only occasionally after that(like VOR check). My other ign is an Emag off the BATT buss.
 
Push buttons

I went through the same thought process a few months back. We use CBs as switches on many items on the B-767, Data link, TCAS, voice recorder, these are pulled between every overnight or long sit, so I was thinking along he same lines as you. But in the end I installed N.C. pushbuttons, just push and this removes the power release and it springs back.

19rpxl.jpg
 
The airlines use breakers for switches all the time. I am trying to imagine how often I will test the p-mags. If only once a week or month then I don't see the need for switches. If every flight then maybe.
 
Once in a while

Tony,

I know what you are saying, I am not flying but my guess is most do this test once in a while not every flight. I put in the switch because I did not have faith the Klixon breakers I am using would be as robust as we have in the big jets. In the end, I actually think using the CB for the test would be fine. The switches were a convenience for me as they are spring loaded you have to hold them on, so I skipped the idea of using the breakers as switches.

The push button switches I bought were about $9 each and fit the same hole as the other toggles.

Cheers
 
RVG8tor said:
Tony,

I know what you are saying, I am not flying but my guess is most do this test once in a while not every flight. I put in the switch because I did not have faith the Klixon breakers I am using would be as robust as we have in the big jets. In the end, I actually think using the CB for the test would be fine. The switches were a convenience for me as they are spring loaded you have to hold them on, so I skipped the idea of using the breakers as switches.

The push button switches I bought were about $9 each and fit the same hole as the other toggles.

Cheers
Click to expand...

I hear you. 767's use Klixon breakers if my memory is correct. Probably higher quality though than the $20 Stein version.
 
Here's your downside.

There's no way to shut off a P-mag if it's generating its own juice, which the later versions do above 900rpm, as they remain on internal supply even if ship's power is disconnected. So if one looses timing, it could very well keep making errant sparks and shake your engine/airplane to pieces and/or drastically reduce power output, bringing about a forced landing even though you have a second good ignition.

Those test switches ground the P-mag, so even if the electronics are still running (properly or not), it won't make a spark. Simply removing ship's power doesn't necessarily shut it down.

Been there, done that. I'm certainly glad I could shut down the bad P-mag.

John Siebold
 
I don't think so. The P-lead switches ground the P-mag to prevent and/or allow spark generation. No matter what the source of power is to the P-mag if the P-lead (ignition) switches are off the P-mag will not spark. The test switches only provided the ability to disconnect aircraft power from the P-mag. For the lager models this test would need to be done at low RPM (below 900 rpm) otherwise as you state, the internal gen will maintain power to the p-mag.
 
Ken,

I may be making a mountain out of a mole hill, as this thread's starter doesn't address whether he has a P-lead switch or not; if he does, all's well, and I'll just back out of this thread 'cause I don't care what kind of switch/breaker/test switch is on the +12. Otherwise, my comment applies. Then, the picture of the pushbutton installation doesn't show a P-lead switch. Hopefully, there's one somewhere else on that aircraft.

So we agree. The test switch depicted is in the +12 line. If the P-mag is running on internal alternator, the only was to kill it is to ground the P-lead, or reduce power to idle (or less than 900 or so when airborne - good luck!). Brad at E-mag told me that the only thing the P-lead does is shut down spark; the electronics are unaffected.

John Siebold
 
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I am still trying to wrap my head around the P-mag principal of operation. Seems that when the P-mag detects a loss of ships power and the engine RPM is over 800, the P-mag internal alternator is activated thus self-powering. The test switches disconnect ships power as would pulling the circuit breaker. There would be no difference in the effect on the P-mag. If the P-mag suffered an internal fault the test switches or circuit breaker would kill ships power and isolate the mags from ship power. The P-lead should kill the P-mag through the ignition switch. You can kill Left or Right P-mag selectively through the ignition switch. Am I mis-understanding this. The ignition switch must provide the isolation of run-away P-mag otherwise there would a major design flaw.
 
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from the P-mag perspective you are correct in that if breakers and test switches are in series then it wouldn't matter which one you used to disconnect power to the P-mag. The issue then becomes one of reliability of using breakers as switches. The later model P-mags (114s) above 800-900rpm are always running on the internal gen even if aircraft power is still available.

And I agree with the earlier post, if P-lead switches are not installed then spark would occur no matter what you did above 800-900 rpm (provided the internal gen was functioning). Although this set-up would be contrary to the installation instructions and am not sure why anyone would do that?
 
Still comes back to how often do you need to test the p-mag. Here is the endurance info for model 7274 breaker from www.klixon.com:

2500 cycles ................................. 120 VAC, 400 Hz Inductive
5000 cycles ................................. 120 VAC, 400 Hz Resistive
2500 cycles ................................. 30 VDC, Inductive
5000 cycles ................................. 30 VDC, Resistive
5000 cycles ................................. Mechanical, no load

Assuming the worst case you would be able to use the breakers about 2500 times before rated failure (probably get 5000). Probably just change the breakers at engine overhaul.
 
There is P-lead switch

If you look at my picture again you will see there is one toggle and one push button test switch for each mag. The toggle controls P-lead (spark) and the push button is a momentary switch to remove ships power for the internal alternator check.

If I need to disable a mag due to lost timing the I can turn it off with the toggle. I cam also permanently remove 12v ships power bu pulling the respective CB.

Funny I thought my labels spelled out the operation clearly but then I guess you have to understand how the P-Mag works.

Cheers

RV7ator said:
Ken,

I may be making a mountain out of a mole hill, as this thread's starter doesn't address whether he has a P-lead switch or not; if he does, all's well, and I'll just back out of this thread 'cause I don't care what kind of switch/breaker/test switch is on the +12. Otherwise, my comment applies. Then, the picture of the pushbutton installation doesn't show a P-lead switch. Hopefully, there's one somewhere else on that aircraft.

So we agree. The test switch depicted is in the +12 line. If the P-mag is running on internal alternator, the only was to kill it is to ground the P-lead, or reduce power to idle (or less than 900 or so when airborne - good luck!). Brad at E-mag told me that the only thing the P-lead does is shut down spark; the electronics are unaffected.

John Siebold
Click to expand...
 
RV7ator said:
Ken,

I may be making a mountain out of a mole hill, as this thread's starter doesn't address whether he has a P-lead switch or not; if he does, all's well, and I'll just back out of this thread 'cause I don't care what kind of switch/breaker/test switch is on the +12. Otherwise, my comment applies. Then, the picture of the pushbutton installation doesn't show a P-lead switch. Hopefully, there's one somewhere else on that aircraft.

So we agree. The test switch depicted is in the +12 line. If the P-mag is running on internal alternator, the only was to kill it is to ground the P-lead, or reduce power to idle (or less than 900 or so when airborne - good luck!). Brad at E-mag told me that the only thing the P-lead does is shut down spark; the electronics are unaffected.

John Siebold
Click to expand...

Yes, I have a standard ACS ignition switch. And you're right there would be no-way to kill a runaway P-mag without.
 
RVG8tor said:
If you look at my picture again you will see there is one toggle and one push button test switch for each mag. The toggle controls P-lead (spark) and the push button is a momentary switch to remove ships power for the internal alternator check.

If I need to disable a mag due to lost timing the I can turn it off with the toggle. I cam also permanently remove 12v ships power bu pulling the respective CB.

Funny I thought my labels spelled out the operation clearly but then I guess you have to understand how the P-Mag works.

Cheers
Click to expand...

Your panel looks great. And yes, your P-mag set up is textbook.
 
apkp777 said:
I am still trying to wrap my head around the P-mag principal of operation. Seems that when the P-mag detects a loss of ships power and the engine RPM is over 800, the P-mag internal alternator is activated thus self-powering. The test switches disconnect ships power as would pulling the circuit breaker. There would be no difference in the effect on the P-mag. If the P-mag suffered an internal fault the test switches or circuit breaker would kill ships power and isolate the mags from ship power. The P-lead should kill the P-mag through the ignition switch. You can kill Left or Right P-mag selectively through the ignition switch. Am I mis-understanding this. The ignition switch must provide the isolation of run-away P-mag otherwise there would a major design flaw.
Click to expand...

Tony,

This is true for the 113 series. The 114's switch to self power whenever they produce enough power. Usually above 800 rpms. Check the electrical page of my web site for how I test my 113's.

For 114's here is how I would test them.
Power on both.
1800 rpm
Turn left off, back on, turn right off. Note rpm drop.
With only the left mag on throttle back until below 800 rpm. (You just tested both internal and external power on the left.)
Turn the right on and left off while still below 800 rpm. Bring it up above 1000 rpm. (You just tested the other Pmag on both ship's and internal power.
Turn on the other mag and go fly.
 
N941WR said:
Tony,

This is true for the 113 series. The 114's switch to self power whenever they produce enough power. Usually above 800 rpms. Check the electrical page of my web site for how I test my 113's.

For 114's here is how I would test them.
Power on both.
1800 rpm
Turn left off, back on, turn right off. Note rpm drop.
With only the left mag on throttle back until below 800 rpm. (You just tested both internal and external power on the left.)
Turn the right on and left off while still below 800 rpm. Bring it up above 1000 rpm. (You just tested the other Pmag on both ship's and internal power.
Turn on the other mag and go fly.
Click to expand...

Bill - Is there any noticeable engine indication when the P-mag switches from self to ships power?

Are you using "test" switches? Your procedure above looks to be a fully functional test of the P-mags with no test switch.
 
apkp777 said:
Bill - Is there any noticeable engine indication when the P-mag switches from self to ships power?

Are you using "test" switches? Your procedure above looks to be a fully functional test of the P-mags with no test switch.
Click to expand...

Tony,

I have 113 Pmags which run off ship's power all the time, unless there is a problem, then they switch to internal power. That's why my preflight test is so complex.

To answer your first question, there is no indication from either the 113 or 114 as to where they get their power from.

The EICommander we make only tells you the CPU voltage, not where those volts are coming from. The Pmag doesn't put out that info. However, we can tell you if we can talk to each Pmag or not. That is not perfect but it is close.

Give me a call, if you have any questions.
 
Keep the erganomics standard!

Tony, at the risk of confusing I have a different approach to wiring and testing the P-mags. I wanted the operation to be as conventional as possible. Take a look here. You end up with just two mag switches, see here, just above the intercom on the right. I dont like the airliner look or erganomics. If on the ground you need the master on and the p-mags 'off', just pull the fuse.

Bill, you said you test at 800rpm. I am doing this from memory but i seem to remember that mine did not quit until considerably slower than that. I'll check next time I fly,
 
Steve Sampson said:
...
Bill, you said you test at 800rpm. I am doing this from memory but i seem to remember that mine did not quit until considerably slower than that. I'll check next time I fly,
Click to expand...

Steve,

No, I said (or meant) "around 800 rpm". They are all slightly different, each person will have to test their own installation to find when they drop out.
 
Bill, I just wrote you an email offline, but I'm going to ask here, too, to see if I can get anyone else's opinion.

You describe a run-up procedure for the 114 Pmags that checks both ship's power and internal power, but includes some throttle jockeying.

Would the following work?

1) Prior to the run-up (still at IDLE less than your "around" 800 RPM), do a mag check (one side, then the other). You've tested the ship's power.
2) Throttle 1700RPM
3) Do another mag check (one side, then the other). You've now tested the internal power.

I think this accomplishes the same thing, with less power changes.

Does anyone see a problem with this?
 
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OFF/ON/TEST

I used a type of DPDT...found the schematics somewhere in the forums. I've got one swith for each PMag...Off / On / Test (Momentary UP position). so my preflight is simply a push up to check the self generation...then if a need to turn a bad PMag off...down to OFF.

Let me know if you are interested in this switch set-up...I'll track down the schematic.

-BC
 
N999ZA said:
Would the following work?

1) Prior to the run-up (still at IDLE less than your "around" 800 RPM), do a mag check (one side, then the other). You've tested the ship's power.
2) Throttle 1700RPM
3) Do another mag check (one side, then the other). You've now tested the internal power.

I think this accomplishes the same thing, with less power changes.

Does anyone see a problem with this?
Click to expand...


My understanding of the 114's is that you would not be able to verify "internal" power (even at 1700 RPM) unless you could absolutely remove the ships power (test switch, breaker, master, etc). Since you can't tell which souce is driving the ignition, you can only force the issue by running below the internal cutoff speed or removing external power.

I have dual 113's on mine and I use the standard key for ignition isolation, and the ships master switch as my "test" switch. Though I rarely test the internal power function any more, it takes only seconds to completely isolate and test each unit.
 
Toobuilder said:
My understanding of the 114's is that you would not be able to verify "internal" power (even at 1700 RPM) unless you could absolutely remove the ships power (test switch, breaker, master, etc). Since you can't tell which souce is driving the ignition, you can only force the issue by running below the internal cutoff speed or removing external power.
...
Click to expand...
Very true. Even with the EICommander we can tell you the voltage on the P-mag's board but not where that voltage is coming from. That information is just not availble.
 
Going out on a limb, would it be safe to say the P-mag would not put out 14v
When checking on the internal power with the commander
 
tadsargent said:
Going out on a limb, would it be safe to say the P-mag would not put out 14v
When checking on the internal power with the commander
Click to expand...

No, the P-mags don't need 14 V to run. In fact, you can run them on a 9 volt battery for hand proping.
 
Toobuilder said:
My understanding of the 114's is that you would not be able to verify "internal" power (even at 1700 RPM) unless you could absolutely remove the ships power (test switch, breaker, master, etc). Since you can't tell which souce is driving the ignition, you can only force the issue by running below the internal cutoff speed or removing external power.
Click to expand...

N941WR said:
Very true.
Click to expand...

So it sounds like either the 113 or 114 needs either Bill's OFF/INTERNAL/SHIP or John's OFF / ON / TEST type switch setup.

I kind of like the all-the-way-up for normal operation switch position...

It's too bad I don't have more time to think about this...

Oh wait. I've got years to think about this...
 
N999ZA said:
So it sounds like either the 113 or 114 needs either Bill's OFF/INTERNAL/SHIP or John's OFF / ON / TEST type switch setup...
Click to expand...

"Needs?"

Well not exactly. What it "needs" is a means of interupting ships power for an ignition "internal power test"; and it needs to ground the "P-lead" to kill the spark for your normal "mag check". That's the requirement. While the schematic shown works just fine I'm sure, there are many combinations of switches, relays, circuit breakers, or fuses that can be used to meet the power and P lead control requirement. It really boils down to what meets your ideal pilot-vehicle interface requirements. For example, after wiring the Hiperbipe with a "test function" (a C/B), and gaining some experience how often (not very) and what phase of flight (right after engine start) the ignition power is tested, I decided that keeping the PVI "standard" on the RV with a familiar key and a master switch was the best overall solution.

YMMV.
 
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Michael,

You are absolutely right. I didn't mention that my PVI is primarily designed around toggles. I shouldn't have used the words "needs" and "switches" without first specifying that.

I think one of my concerns is using the master switch in a series of on and off positions as the test for removing power to the ignitions. Wouldn't all equipment (including EFIS, ADHARS, electric gyros, etc.) be cycling on and off with this activity?

I suppose it depends on what equipment you have on board. I can imagine a setup where cycling the master doesn't impinge on any boot cycles, etc. (Maybe backup batteries in the EFIS, etc.).

(head explodes from thinking about all the possibilities)
 
N999ZA said:
Michael,


...I think one of my concerns is using the master switch in a series of on and off positions as the test for removing power to the ignitions. Wouldn't all equipment (including EFIS, ADHARS, electric gyros, etc.) be cycling on and off with this activity?..
Click to expand...

It depends upon how much equipment you have on line at engine start, but yes, you may "boot up" twice. I tend to run minimal equipment at engine start anyway, but the -8 has the GRT displays which don't mind this activity (if what I read on this forum is right). I also have the option of leaving the EFIS/EMS off for engine start because I have added a discrete oil pressure warning lamp. Oil pressure is my only concern on start, so having the displays blank does not bother me in the least.

On start, I simply verify oil pressure (lamp out), then set the RPM to a fast idle (above cutoff speed) by ear. I then cut the master switch - if the engine quits, both ignitions have failed to make internal power and the flying is over for the moment - if not, then I do a quick mag check to isolate each mag looking for a single ignition internal failure. If the engine keeps running in L and R position, I have performed the "test" function for each ignition - all within 30 seconds of engine start. After that it's Master ON, Alternator ON, and continue with the boot up process.

Yes, with the master off the oil pressure light is inactive, but the odds of having an oil pump failure in the few seconds it takes to turn the key through L/R/Both is way too low to be on my radar.
 
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That's way less clunky of a flow than I thought it would be.

(Hmm, that was supposed to be a compliment. Sorry if it didn't sound like it.)

Just thinking out loud, maybe an "e-bus armed" switch (if you go with that architecture) might keep an EMS on through the test if that's what one deems to be required throughout the start...

Master on, e-bus armed, start the engine, master off, do the checks you describe, all the while the e-bus is powering the EMS.

Although some people power their EIs from the e-bus. Hmm... scratch that.
 
Isn't there an issue with cycling the alternator while the engine is running that can kill them?
 
N999ZA said:
That's way less clunky of a flow than I thought it would be.

(Hmm, that was supposed to be a compliment. Sorry if it didn't sound like it.)
Click to expand...

Compared to some of the comments I've received before, your response is downright gushing! ;)


N999ZA said:
Just thinking out loud, maybe an "e-bus armed" switch (if you go with that architecture) might keep an EMS on through the test if that's what one deems to be required throughout the start...

Master on, e-bus armed, start the engine, master off, do the checks you describe, all the while the e-bus is powering the EMS.

Although some people power their EIs from the e-bus. Hmm... scratch that.
Click to expand...

IMHO, if keeping the EMS alive for every second the prop is turning is a requirement, then the cleanest, simplest method is to simply make sure the fuses or resettable C/B's are accessable from the pilot's seat and use them as the "test switches". Even if you test the internal power on every flight (highly unlikely once the novelty wears off), you will wear out the airplane long before you kill the C/B's by "inappropriately" using them as switches.
 
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N941WR said:
Isn't there an issue with cycling the alternator while the engine is running that can kill them?
Click to expand...

If there is, I'd like to hear why.

I never start the engine with the alternator on line anyway, so the battery is the only thing that is "cycled" (on and off) with the engine running.
 
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N941WR said:
Isn't there an issue with cycling the alternator while the engine is running that can kill them?
Click to expand...

I thought the warning was against isolating the battery while the alternator is still providing power. Can't remember, though.

Toobuilder said:
Even if you test the internal power on every flight (highly unlikely once the novelty wears off), you will wear out the airplane long before you kill the C/B's by "inappropriately" using them as switches.
Click to expand...

Good point.
 
N999ZA said:
I thought the warning was against isolating the battery while the alternator is still providing power. Can't remember, though.
Click to expand...

Well, isolating the alternator from load (rather than just the battery)...Yes, this is very bad! It's like mashing the gas pedal on your car to the floor with the transmission in neutral... Nowhere for all that output to go. But the alternator switch kills the field - so no output.
 
Toobuilder said:
Well, isolating the alternator from load (rather than just the battery)...Yes, this is very bad! It's like mashing the gas pedal on your car to the floor with the transmission in neutral... Nowhere for all that output to go. But the alternator switch kills the field - so no output.
Click to expand...

There 's a lot of discussion on this in the archives, and frankly, no one has PROVEN anything....but there seems to be a reasonable indication of a correlation between shortened life of the internally regulated ND alternators when switched on while already turning. The argument is that in their automotive application, the field is never switched off while they are turning, and they weren't designed for that. I used to switch on the alternator after start-up, and my first one died at about 250 hours. Second one, I never switched, and it lasted over a thousand. I have seen this correlation with other planes as well.

Since I really had no good reason to switch the alternator off and on with the engine running, I stopped doing it. Might be superstition, but there were some fairly compelling technical arguments a few years back on the topic - look up posts by GMCJETPILOT if you have a lot of time to kill!

Anyway - not trying to convince you one way or the other, just pointing you in a direction for some interesting discussion.

Paul (I plan to test the "power-off" circuit of the P-Mags occasionally by pulling the circuit breakers....)
 
Ironflight said:
...but there were some fairly compelling technical arguments a few years back on the topic - look up posts by GMCJETPILOT if you have a lot of time to kill!...
Click to expand...

Thanks! I'm all over "compelling technical arguments" like a fat kid on cake - particularly if they are contrary to my own behavior. To be honest, I was taught to fly this way and since it did not conflict with my (not insignificant) understanding of alternators, I accepted it.

I?m not sure how charging the field around a spinning rotor is any harder on the unit than subjecting it to the enormous voltage swing created by cranking, and then start of the engine ? but I?ll sure try find out.
 
Toobuilder said:
I?m not sure how charging the field around a spinning rotor is any harder on the unit than subjecting it to the enormous voltage swing created by cranking, and then start of the engine ? but I?ll sure try find out.
Click to expand...

The problem is not so much with the spinning part of the alternator part of the equation - this seems to kill the internal regulator. Just wanted to head you down the right path!

Paul
 
Ironflight said:
The problem is not so much with the spinning part of the alternator part of the equation - this seems to kill the internal regulator. Just wanted to head you down the right path!

Paul
Click to expand...

Well, it's the "spinning" that creates the voltage that the regulator has to deal with... All I was trying to say.
 
I?m not sure how charging the field around a spinning rotor is any harder on the unit than subjecting it to the enormous voltage swing created by cranking, and then start of the engine...
Click to expand...

Having an internally regulated automotive alternator spinning at speed, then switching it on (the field input on this type of alternator just turns on the regulator) results in a large voltage / current spike that the output diodes have to deal with. I have the Delco SI type internal regulator schematic, and the regulator sense circuit control speed is limited by loop filtering / slope integration. The field control does not have filtering. Switching this type of regulator on via the "field" control input will result in full current instantly, followed by a ramp down to the correct output voltage. It simply wasn't designed to be switched on at speed.

Some alternators have output diodes robust enough to deal with this spike and not suffer reliability issues. From personal experience I can tell you that some Delco 10SI units do not. This type of regulator - alternator circuit is designed to start producing current from the first revolution. This results in an intrinsic soft start, as the output at starter rpm is minimal.

The regulator IC can suffer from the field current surge as well (I'm told), though I have not personally experienced this failure mode.

As to the "enormous voltage swing created by cranking", the voltage drops to perhaps 8 volts while cranking, and returns to battery voltage as the engine starts and the starter is disconnected. This doesn't result in any stress to the alternator.

If I was designing a regulator for aircraft use, I would ensure that the regulator circuit could not be switched on in a way that resulted in an initial full field output prior to ramping down to the correct voltage. I'd also specify over rated diodes for the alternator, all for the sake of reliability. One hopes B&C and P.P. have done this.

Some of the latest automotive alternators sense the alternator rpm, keep it off line until a certain rpm is reached (reduces the load on the starter), then soft starts the alternator automatically. There are even schemes where the ECU controls the alternator via a serial bus. Perhaps the Vertical Power team will look into that. :D

Examples of the latest regulators:
L9911.pdf
IRVR101.pdf
 
Thanks for that Ted. I'm pretty familiar with the Delco alternators though my "car" hobby, but never had to think about switching one on/off (obviously). However, research indicates that the B&C CAN take the switching with no problem - as it is designed for just that. However, I realize that just because the alternator is capable of handling the switching does not mean that that is a good reason to do so on a routine basis, so I'll be starting with the field on from now on.

That said, I think the idea of using the master switch as a Pmag "test" switch can still be valid. If a given pilot's only concern is the switching of the alternator "at speed", then I think the fact that the Pmag testing is done so infrequently, coupled with the fact that very few of us are running purely automotive alternators (apparently, the only ones that can't handle the voltage spike), is still better than adding separate switches on the panel. Even the automotive versions seem to be fairly robust, as evidenced by the fact that I am still using the "mock up" 60 amp ND (same as the basis for the B&C unit) that I pulled from the junkyard. After the bracketry was built, I decided to see if this well used unit produced any power, and it has flawlessly for 300 hours now - and suffering the abuse of switching on after start every flight.
 
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